| With the development of human society, environmental pollution and energy shortage have been more and more serious. Over the past several decades, people have been searching one solution that is low cost, highly efficient, and environmentally friendly to deal with these issues. Since Fujishima and Honda discovered photocatalytic water splitting on TiO2 electrodes in 1972, this process has attracted great attention because of its potential for hydrogen production in an environmentally friendly way, which is seen as a promising strategy to ease environmental problems and energy shortage. Solar energy is completely unlimited as well as low cost. Usually, photocatalytic activity can be improved through modifying traditional photocatalysts and exploring novel ones.Compared with oxides, sulfide photocatalysts endow wonderful visible light response ability. For example, CdS, with band gap of 2.4 eV, can response to visible light well. Besides, the conduction band and valence band of CdS are just right to degrade organic pollutants and produce hydrogen from water splitting. However, there are two shortages for CdS. On one hand, the photogenerated electrons and holes can easily recombine, severely limiting its photocatalytic activity; one the other hand, CdS is not stable under light irradiation. Doping is considered as one useful approach to tune the electronic band structure, and thus improve photocataltytic activity and stability. In this work, we successfully prepared Ga interstitially doped CdS and O substituted CdS samples with hydrothermal method.1. Hydrothermal method is an effective and feasible way to prepare doped samples. We prepared Ga doped CdS samples with different Ga/Cd ratio. According to a series of characterization methods, we confirmed the as-prepared samples were Ga interstially doped CdS. The photocatalytic activity of water splitting as well as organic pollutant degradation is highly enhanced. The stability of CdS under solar light irradiation is improved. The photogenerated holes and super oxygen radicals are considered to be reponsible for the photodegradation reaction. The enhanced activity and stability can be attributed to the narrowing of band gap, widening of valence band, and indirect semiconductor nature. These three factors are critically beneficial for the generation of more conduction band electrons and valence band holes, and the effective inhibition photogenerated carrier recombination. We believe Ga-doped CdS will be a promising photocatalyst with richly potential application prospect under solar light.2. Metal-ion-doped CdS has been researched for a long time. However, non-metal-ion doped CdS has never researched before, owing to the lack of efficient doping approaches. In this work, for the first time we successfully prepared oxygen doped CdS via hydrothermal method using Cd(Ac)2, thiourea, and H2O2 as precusors. Through kinds of characterization methods, we confirmed that oxygen atoms indeed came into the CdS lattice, substituting sulfur atoms. The photocatalytic degradation of organic pollutants and water splitting rate of CdS were largely enhanced. We came up with the enhanced mechanism for oxygen doped CdS, based on the photoelectrochemical measurement. The introduction of oxygen in the lattice widen the band gap of CdS, that is, blue shift. The recombination rate of photogenerated electrons and holes can be largely reduced. The conduction band minimum shifted upwards, so that the reductive ability of electrons can be improved. Besides, doping can effectively reduce the residence of charge carriers motivation. It is worthy noting this hydrothermal preparation method can be applied to synthesize oxygen doped In2S3 and ZnS photocatalysts, improving their photocatalytic performance. We believe this work provides a reference for the enhancement of photocatalytic activity of sulfide. |
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